Capcom has been working on Resident Evil 9 for more than two years, according to reputable leaker Dusk Golem.
In a recent string of tweets discussing Capcom's alleged long-term plans, Dusk Golem explained that "there was a period of time that [Resident Evil 2 Remake, Resident Evil 3 Remake, Resident Evil Outrage, Resident Evil 4 Remake, and Resident Evil 9] were all in development at the exact same time (late 2018)."
In a follow-up tweet, they clarified that while Resident Evil 9 is very much a thing, "it's actually not worth even talking about right now" because it's so far out. "I literally cannot see it releasing before 2024," they said.
Last year, Capcom suffered a ransomware attack which leaked the projected launch windows for several unannounced games. Among them was a new Resident Evil project codenamed Resident Evil Hank, which was scheduled for the fourth quarter of the 2024 fiscal year. Whatever it is, this game remains unannounced and its details are unknown, but of the Capcom projects that we know of, this best fits the new rumors around Resident Evil 9.
As Dusk Golem said, it's pointless to speculate about projects that are this far out because any number of things could change by the time we actually hear about them, let alone play them. For comparison, the same timeline which leaked following the attack on Capcom also listed the long-rumored Resident Evil 4 Remake for a Q4 FY2022 release. However, according to a January report, the RE4 remake has been delayed following an internal reboot sparked by a shift in creative vision, and may now arrive as late as 2023.
Dusk Golem previously suggested that Resident Evil Outrage is actually Resident Evil Revelations 3.